gis raster analysis and queries

Question 1

map algebra

Answer 1

A language that defines a syntax for combining map themes by applying mathematical operations and analytical functions to create new map themes. In a map algebra expression, the operators are a combination of mathematical, logical, or Boolean operators (+, >, AND, tan, and so on), and spatial analysis functions (slope, shortest path, spline, and so on), and the operands are spatial data and numbers.

Question 2

boolean overlay

Answer 2

evaluating rasters with Boolean operators to evaluate areas where combinations of specific conditions exsit

Question 3

boolean raster

Answer 3

raster with cells that contain a 1 to indicate true or 0 to indicate false regarding a specified condition

Question 4

euclidean distance

Answer 4

straight line distance between two points

Question 5

interpolation

Answer 5

to calculate values at locations between known measurements: to populate a raster with values extrapolated from a known set of point values

Question 6

surface analysis

Answer 6

functions designed for application to rasters representing a three-dimensional surface, such as elevation

Question 7

neighborhood functions

Answer 7

calculation of a value for a target cell or feature based on surrounding values from a defined region

Question 8

block function

Answer 8

an analyis function that moves over a raster in adjacent, non overlapping neighborhoods.

Question 9

focal function

Answer 9

raster analysis function that determin new values for a target cell based on values in a moving neighborhood around the target. The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell.

Question 10

filter

Answer 10

a moving window applied to araster data layer that calculates new values for the center pixel based on some function of the values in the window. On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but are most commonly three-cell by three-cell squares.

Question 11

zonal statistics

Answer 11

raster analysis functions that calculate statistics from one raster for zones defined by a different raster. ] In ArcGIS Spatial Analyst, the calculation of a statistic for each zone of a zone dataset based on values from another dataset, a value raster. A single output value is computed for each cell in each zone defined by the input zone dataset.

Question 12

reclassify

Answer 12

to replace sets or ranges of values in a raster witj different sets or ranges

Question 13

resampling

Answer 13

to change the resolution of a raster using a defined strategy to convert values from one cell grid to another

Question 14

nearest neighbor

Answer 14

a resampling method for discrete data that grabs the closest value to a cell center

Question 15

bilinear

Answer 15

resampling method that interpolates a new cell value based on the four closest values

Question 16

cubic convolution

Answer 16

resampling method that interpolates a new cell value from the 16 closest input cells

Question 17

grid

Answer 17

specific raster format native to GRID and Spatial Analyst; generic term for a raster data set

Question 18

zone

Answer 18

the combined area of a raster that share the same attribute value, such as all areas with the commercial land use code

Question 19

noDAta

Answer 19

special value used to designate that a data value is absent or unknown

Question 20

azimuth

Answer 20

measurement of compass direction in 360 with 0 = north

Question 21

zenith angle

Answer 21

angular measure of the distance of an object above the horizon

Question 22

spatial join

Answer 22

a function that combines the attributes of features in two layers based on containment or distance

Question 23

summarized join

Answer 23

a join that combines the records of two attribute tables with a one-to-many cardinality by assigning each output record a single value derived statistically from the many input values

Question 24

simple join

Answer 24

a join that combines two layers according to common locations when a one-to-one spatial relationship exists between the layers

Question 25

logical consistency

Answer 25

a measure of well data features represent real world features, in particular with respect to topology